Preterm birth (PTB) remains a major public health problem, complicating >10% of all deliveries, and its associated perinatal morbidity and mortality represents 30% of the total. The greatest single risk factor for PTB is a prior PTB. Early and accurate identification of at risk patients may permit targeted interventions. Despite great effort, the US PTB rate has actually increased over the past 30y. This failure reflects a poor understanding of the basic mechanisms initiating PTB coupled to a long held assumption that preterm labor (PL) is simply term labor ill timed. Ascending infection from the lower genital is a well-recognized as a mechanism of upper tract inflammation, fetal inflammatory response syndrome, decidual hemorrhage, chorioamnionitis or combinations thereof. Yet, antibiotic therapy has failed to reduce the PTB rate. It is likely other therapeutic strategies are necessary once the innate immunity of the lower genital tract is overwhelmed and the inflammatory cascade established in the upper genital tract or fetal compartment. We hypothesize that PTB reflects an alteration of oxygen independent (defensins and calgranulins) and oxygen dependent (oxygen free radicals) defense mechanisms of the lower and upper genital tract, and that the sequestration of certain polymorphisms in genes regulating the inflammatory cascade among some ethnic groups accounts in part for their risk of recurrent PTB (Specific Aim 1a). We hypothesize women destined for PTB express cervicovaginal biomarkers illustrative of altered innate immunity weeks or months before onset of PTB symptoms (cervical ripening, preterm labor contractions or pPROM) that can be reliably identified using proteomic tools (Specific Aim 1b). We hypothesize that the progesterone compounds reported to decrease recurrent PTB affect maternal lower and upper genital tract defense mechanisms as well as the fetal inflammatory response axis (Specific Aim 2). This proposal brings together an experienced multidisciplinary team who will test elements of these hypotheses in experiments performed over a 5y period.